A process and two-step catalytic reactor system for the production of liquid hydrocarbons from plastic waste

ABSTRACT

The present invention relates to a process and a system for the production of liquid hydrocarbons by thermo-catalytic cracking of plastic waste. The invention relates to a technique for efficiently producing high-quality liquid fuel using designed reactor setup for the cracking of waste plastic. The invention also relates to a thermo-catalytic cracking method, which occurs in the presence of zeolite-based catalysts, more preferably the zeolite catalysts impregnated with transition metals which remain catalytically active up to 8-10 sets of reactions with higher selectivity of petroleum range hydrocarbons. The present invention also relates to a two-step approach system for the production of liquid hydrocarbons.

FIELD OF INVENTION

The present invention relates to a process and a system for the production of liquid hydrocarbons by thermo-catalytic cracking of plastic waste.

BACKGROUND OF THE INVENTION

The production of plastic materials has greatly increased in the past decades, leading to the parallel rise in the plastic waste generation. The invention of plastics has brought convenience to day to day life. They meet up the need of fast-growing world population for cost-effective, energy-efficient, environmentally benign materials with low greenhouse gas emissions (“carbon footprint”), low weight, and versatility in terms of tailoring properties, applications, and recycling. The greatly diversified applications of polymers range from packaging, permitting safe supply of food and medicine, low weight engineering plastics for the application of automotive and architectural purpose, rubbers, textiles, thermal and electrical insulation, for earthquake-proof pipes and casing for the safe transport of gas and water.

In ideal way, advance-polymers meet the requirements for both green chemistry and sustainable development. Polymers are the high molecular-mass hydrocarbon materials that possess oil-like energy content; which are manufactured through an energy-efficient, exothermic catalytic process that produces a substantial quantity of energy. Therefore, recycled plastic wastes serve as a valuable source of energy and hydrocarbon feedstock. By performing the thermal cracking of C—C bonds above 300° C. temperature, polymers easily degrade to form the low molecular-mass hydrocarbons, thus forming oil and gas feedstock with high quantitative yields. Polymers are believed to meet the demands of sustainable development, and thus meeting the current energy demand devoid of compromising the capability of future generations to fill up their own demands for energy.

The plastics are sound way categorized into seven different classes. Furthermore, waste plastics are found in various forms; such as in bulk amount of precisely identified plastic materials which are generated as a waste in the plastic industry whereas other forms are considered as the discarded matter and containers. In reference to the developed countries, for the process of plastic recycling; the polymers taken into account are the ‘process scrap’ from the industries generated during the production of plastics. In this context, plastic recycling is relatively simple and economically feasible, as the material to be recycled is moderately contaminated. It is typically considered as reprocessing rather than recycling. Daily household chores are the principal source of waste plastic. There are number of challenges in the recycling of household plastics. The one amongst them relates to the collection done by hand. However, post categorization, the plastic is melted down the straight line and molded into a fresh shape or else melted down after shredding and later on processed into granular particles.

In the feedstock or chemical recycling process, feedstock recycling describes a variety of plastic recovery methods which again form the fresh plastic material by the process of cracking of polymers into their respective monomers, which have the direct application in the refineries and petro-chemical production. Nowadays, a series of feedstock recycling technologies are being explored which includes mainly the processes such as, Pyrolysis, Hydrogenation, Gasification, Thermal cracking, and Catalytic cracking. Feedstock recycling shows efficient flexibility over the product distribution and can be considered as more tolerant towards the impurities than the mechanical recycling. However, it is believed to be the least economic process due to its huge capital investment.

In addition, while if the thermal cracking of the waste plastic is considered, the molten material formed during thermal cracking has comparatively high viscosity and hence, higher operating temperature needed for its execution. However, for the catalytic cracking of the same; the deactivation of the catalyst is the major challenge due to the impurities present in waste material.

There are around 50 different groups of plastics with wide variety of products. Each and every type of plastic is recyclable. In regard to make the segregation and recycling easy, the American Society of Plastic Industry has developed a standard marking code for the customers to identify and sort the types of plastics. Prior to the recycling process, the waste plastics are sorted based on their unique resin identification code which distinguishes their applications with chemical and physical properties.

Traditionally, the thermal cracking (pyrolysis) and catalytic cracking are employed for the recycling of waste plastics which promotes the formation of significant amount of C1-C5 gases and some high molecular weight liquid hydrocarbons that are not suitable to be used as fuel like liquid source. The above-mentioned processes produce majorly the lighter gases, carbon black, and fuel like liquids. However, the formation of carbon black and lighter gases in major fraction is undesirable. As a result, there is a great need of the development of the improved processes which can contribute towards the production of comparatively higher yield of liquid hydrocarbons from the waste plastic or the discarded plastic. The proposed invention can be of great benefit to the small-scale facility.

There are several patents and publications available in the art with various methodologies for thermal and catalytic cracking of waste plastics. For example, U.S. Pat. No. 3,923,472, U.S. Pat. No. 3,947,256, U.S. Pat. No. 3,996,022, U.S. Pat. No. 4,145,188, and U.S. Pat. No. 5,082,534 are few prior arts which disclose different processes and methods for waste plastic conversion into liquid fuels.

U.S. Pat. No. 4,746,406, U.S. Pat. No. 5,230,777, U.S. Pat. No. 5,230,777, CN 102,942,951, U.S. Pat. No. 6,066,263, CN101,928,585, JP 2006,056,957, JP 2004,083,795, CN 101,463,265, IN/PCT/2002/1137IKOL, WO2013/169367 and U.S. Pat. No. 6,143,940 also discloses various processes for conversion of plastic waste into oil or hydrocarbons.

Santos et al, discloses thermal and catalytic pyrolysis of urban plastic waste composed mainly of the polypropylene and polyethylene. Catalytic pyrolysis using alkaline zeolites were found to give the higher amounts of the liquid fraction. Both the thermal and catalytic pyrolysis was performed at 450° C. under the nitrogen flow rate of 10 mL/min for 30 min. The catalysts employed were the USY and alkaline zeolites for the catalytic cracking of mixture PP:PE in the ratio of 1:1 using batch reactor. The plastic and the catalyst mixture were fed directly to the reactor leading to the simultaneous heating of the polymer and catalyst. However, the plastic mixture and the catalyst fed to the reactor at the same time and thus, allowing the immediate contact of polymer melt with the catalyst surface. Thereby, favoring the carbon black formation on the catalyst surface and leading to the fast deactivation of the catalyst. Also, the use of alkaline zeolites favors the formation of gaseous fraction majorly at these high operating temperatures; and thus, the process becomes less beneficial from the economic point of view.

Kunwar et al, discloses production of synthetic gasoline and diesel fuels via catalytic and non-catalytic pyrolysis of waste polyethylene and polypropylene followed by distillation of plastic crude oils. Reactions were optimized using the batch reactor to produce fuel range compounds. Pyrolysis of the polypropylene was carried out at 500° C. for 2 hours of the total reaction time; wherein, the catalytic cracking was performed in the presence of MgCO₃ at 500° C. The feed has the ratio of catalyst to polyethylene in the range of 1:10 for the catalytic cracking. Furthermore, the yield for the plastic crude oil obtained were 69%, 46% and 43% at the temperature of 500, 525 and 550° C. respectively. However, as the operating temperature is high, the process becomes energy intensive in case of catalytic cracking of polypropylene.

Vas et al discloses thermo-catalytic cracking for polypropylene in the fixed bed reactor system. The process of thermal and catalytic cracking is believed to occur at the similar conditions; as the reactor have a mixture of polymer (PP) and the catalyst (Zeolite) operating at the optimized reaction conditions. The key factors responsible for product formation are given as, Zeolite: PP ratio of 1:5, the N₂ flow rate of 9 L/H, reaction duration 78 min, operating temperature 467° C. At the same time, they also showed that when the catalyst to polymer ratio was increased to 1:2.5 the reaction temperature got lowered with increase in the liquid yield. In brief, the article has incorporated very high catalyst usage at quite a higher temperature. The reaction duration for the complete conversion of solid to liquid is very high. As the polymer and catalyst are getting heated simultaneously in the furnace, the catalyst is prone to very fast deactivation by coke formation on its surface. Moreover, the reaction time of 3-4 hours is quite high for the operating temperature of 425° C. The process is substantially less effective for the commercial purpose.

Cleetus et al discloses catalytic pyrolysis of polyethylene in a fixed bed reactor set up. The reactor system has the ceramic unit for pyrolysis followed by the condenser and sample collector. In similarity to the article D1, the heating zone has the mixture of polymer and catalyst reacting at a temperature of about 425° C. The feed has the ratio of zeolite to polyethylene in the range of 1:4 indicating very high usage of the catalyst. The reaction duration of around 3-4 hours was reported to be the optimum time for the product formation.

As the polymer and catalyst are getting heated simultaneously in the furnace, the catalyst is prone to very fast deactivation by coke formation on its surface. Moreover, the reaction time of 3-4 hours is quite high for the operating temperature of 425° C. The process seems to be less effective for the commercial purpose.

Muhammad et al discloses thermal degradation of waste plastics comprising PP, PE, PS, and PET in a two-stage pyrolysis catalysis reactor for the fuel production. The thermal cracking leads to the formation of volatiles which can pass through the catalytic zone of zeolite (HZSM-5) for further cracking. The reaction temperature of around 500° C. was reported to be the optimized one for the thermal as well as catalytic zone. The volatiles are allowed to pass through catalytic bed which was preheated for 30 min, so the volatiles are directly allowed to come in contact with the catalyst. This leads to the liquid fuel formation with lower molecular weight having hydrocarbons in the range of C5-C15. In this case, the usage of the catalyst is very high i.e. the ratio of plastic to zeolite used is around 1:1. The selectivity for the liquid obtained is given around 45-51% with considerable production of uncondensed gases.

The processes of prior arts for the use of plastic waste in the production of value added chemicals by exercising various techniques have presented several problems. This majorly contributes to the problem associated with the coke formation on the surface of the catalyst and thus, inhibiting the catalytic activity for the production of fuel-range of compounds. Over a very short interval of time, the catalyst is deactivated as the waste plastic melt has considerable impurities in it which leads to the coke formation and thus the catalytic material gets deactivated for the particular cycle.

Therefore, it is crucial to develop environmentally friendly waste plastic to hydrocarbon oils or fuels with high catalytic activity retention and most importantly to overcome the coke formation on the surface of the catalyst.

OBJECT OF THE INVENTION

Therefore, it is an object of the present disclosure to overcome the problems in the prior art. One of the major objectives of the present invention is to provide an easy and compact recycling system for the production of fuel like liquid from waste plastics eventually leading to the cost savings and ease of maintenance whereas contributing higher yield and greater economy.

SUMMARY OF INVENTION

The present invention aims to provide a novel approach for the utilization of waste plastic by converting them into the fuel-range products capable of being used as a fuel source in place of the petro-diesel products at the temperature below 400° C. with high liquid yield (60-80%) by using minimal amount of catalyst. In particular, the present invention relates to a process and a system for efficiently producing high-quality fuel-like hydrocarbons using designed reactor setup for the cracking of waste plastic. In addition, the thermo-catalytic cracking occurs in the presence of zeolite-based catalysts, more preferably the zeolite catalysts impregnated with transition metals which remain catalytically active up to 8-10 set of reactions with higher selectivity of petroleum range hydrocarbons.

In an embodiment, a process for the production of hydrocarbons from plastic waste is provided. The process according to the present invention comprises the steps of: (i) thermally cracking the plastic waste in a thermal cracking zone (120) at a temperature of about 200 to 400° C. forming hydrocarbon vapors (122); (ii) catalytically cracking said hydrocarbon vapors in a catalytic cracking zone (130) using zeolite catalyst impregnated with transition metals selected from the group consisting of Fe, Cu, Co, and/or Ni at a temperature of about 300 to 400° C.; and (iii) condensing the hydrocarbon vapors at a temperature of about −5 to about 15° C. forming fuel-like hydrocarbon having C5 to C28 hydrocarbon fractions; wherein 60-80% of fuel-like hydrocarbon formed are liquids and 20-35% are gases.

The zeolite catalyst according to the present invention can be impregnated with copper or iron. The ratio of the catalyst to plastic waste can be in the range of 1:10 to 1:30.

The process according to the present invention produces fuel-like hydrocarbons preferably that have C5 to C18 hydrocarbon fractions. The fuel-like hydrocarbon of the present invention has a calorific value in the range of 42 to 45 MJ/kg.

In an embodiment, the thermal cracking and catalytic cracking reaction can be completed in 10 to 25 minutes. The catalyst retains reactivity for about 8-10 sets of reactions.

The process according to the present invention, further comprises the steps of separating, sizing, pelletizing and/or processing the plastic waste prior to thermal cracking.

In an embodiment, a two-stage batch reactor system (100) for producing a fuel-like hydrocarbons from plastic waste is provided. The two-stage batch reactor system comprises (i) a thermal cracking zone (120) adapted to receive plastic waste; (ii) a catalytic cracking zone (130) arranged vertically and connected to said thermal cracking zone (120) and comprising zeolite catalytic bed (132); wherein the zeolite catalyst is impregnated with a transition metal selected from the group consisting of Fe, Cu, Co, or Ni; and (iii) a condenser (140) connected to said catalytic cracking zone (130) maintained at about −5 to about 15° C. temperature range.

The catalytic cracking zone (130) can be arranged vertically about 20-30 mm above the thermal cracking zone (120) such that there can be an immediate interaction of vapor from the thermal cracking zone and the catalyst bed. An inert gas cylinder (110) supplies inert gas to the thermal cracking zone (120). The system according to the present invention further comprises a hydrocarbon gas collector (150) and a hydrocarbon liquid collector (160) connected to said condenser (140).

BRIEF DESCRIPTION OF DRAWING

FIG. 1 depicts the process steps of the present invention.

FIG. 2 illustrates the block diagram of the process of production of liquid fuel from waste plastic for the present invention.

FIG. 3 illustrates the batch reactor system following a two-step approach for the thermo-catalytic cracking of waste plastic.

DETAILED DESCRIPTION OF THE INVENTION

The following is a detailed description of embodiments of the invention. The embodiments are in such detail as to clearly communicate the disclosure. However, the amount of detail offered is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present invention as defined by the appended claims.

Each of the appended claims defines a separate invention, which for infringement purposes is recognized as including equivalents to the various elements or limitations specified in the claims. Depending on the context, all references below to the “invention” may in some cases refer to certain specific embodiments only. In other cases, it will be recognized that references to the “invention” will refer to subject matter recited in one or more, but not necessarily all, of the claims. Unless the context requires otherwise, throughout the specification which follow, the word “comprise” and variations thereof, such as, “comprises” and “comprising” are to be construed in an open, inclusive sense that is as “including, but not limited to.”

Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the content clearly dictates otherwise. It should also be noted that the term “or” is generally employed in its sense including “and/or” unless the content clearly dictates otherwise.

All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g. “such as”) provided with respect to certain embodiments herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention otherwise claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention.

The title and abstract of the invention provided herein are for convenience only and do not interpret the scope or meaning of the embodiments.

The following discussion provides many example embodiments of the inventive subject matter. Although each embodiment represents a single combination of inventive elements, the inventive subject matter is considered to include all possible combinations of the disclosed elements. Thus, if one embodiment comprises elements A, B, and C, and a second embodiment comprises elements B and D, then the inventive subject matter is also considered to include other remaining combinations of A, B, C, or D, even if not explicitly disclosed.

Various terms as used herein are shown below. To the extent a term used in a claim is not defined below, it should be given the broadest definition persons in the pertinent art have given that term as reflected in printed publications and issued patents at the time of filing.

The present invention relates to a two-step approach to control the immediate deactivation of the catalyst, as instead of plastic melt, hydrocarbon vapors will interact with the catalyst surface at the temperature below 400° C. with high liquid yield (60-80%) by using substantially minimal amount of catalyst. The developed two step approach leads to substantially 100% conversion of plastic waste into value added products comprising 60-80% liquids, and 20-35% gases.

Moreover, the current invention promotes the gasoline and diesel fraction formation from the waste plastic in considerable amount and efficient manner. By this means, it contributes towards resource reclamation and environment protection.

In an embodiment, the present invention provides a process for the production of hydrocarbon from plastic waste is provided. The process according to the present invention comprises the steps of: (i) thermally cracking plastic waste in a thermal cracking zone (120) at a temperature of about 200 to 400° C. forming hydrocarbon vapors; (ii) catalytically cracking said hydrocarbon vapors with a zeolite catalyst impregnated with a transition metals selected from the group consisting of Fe, Cu, Co, and/or Ni in a catalytic cracking zone (130) at a temperature of about 300 to 400° C.; and (iii) condensing the hydrocarbon vapors at a temperature of about −5 to about 15° C. forming fuel-like hydrocarbon having C5 to C28 hydrocarbon fractions; wherein 60-80% of fuel-like hydrocarbon formed are liquids and 20-35% are gases.

In a preferred embodiment, the zeolite catalyst can be impregnated with copper or iron. The as synthesized zeolite catalyst impregnated with transition metal plays a crucial role in tuning the fraction of hydrocarbons formed. The usage of the zeolite catalyst impregnated with transition metal shows an added advantage of reducing the cracking temperature as well as tailoring the selectivity. In an embodiment, the temperature of the catalyst bed in the catalytic zone can be maintained between 100-400° C. for the further cracking of thermally cracked vapors. Preferably, the ratio of the catalyst to plastic waste can be in the range of 1:10 to 1:30. The lower consumption of catalyst was one of the challenges in the catalytic cracking of plastic. The present invention shows that a minimal ratio of zeolite to a polymer (1:10-1:30) was found to be efficient for the reaction.

In an embodiment, the thermal cracking and catalytic cracking reaction can be completed in 10 to 25 minutes. The catalyst retains reactivity for about 8-10 sets of reactions. Thus, the present invention provides substantially faster means for the formation of fuel like liquid. Further, the catalyst has delayed the coke formation on its surface with good recyclability, and hence the process is cost effective as well.

The process of the present invention further includes the steps of separating, sizing, pelletizing and/or processing the plastic waste prior to thermal cracking.

FIG. 2 shows the block diagram describing the process of the present invention. In a preferred embodiment, the plastic waste, such as those sourced from municipal solid waste (MSW) can be used as a raw material for the process of the present invention. Preferably, the plastic material used in the invention can have a composition of polypropylene (PP), low-density polyethylene (LDPE), and high-density polyethylene (HDPE) which can account for about 50% of the total municipal plastic waste. The MSW from a storage (Block 1) is separated (Block 1A) sized and pelletized (Block 2B) and supplied to a shredder where the plastic waste is shredded and pelletized (Block 2). The shredded and pelletized is fed (Block 3A) to thermal cracking (Block 4) through a hopper (Block 3). Thermal cracking of the plastic waste is carried out in a thermal cracking zone (4, FIG. 3) at a temperature of about 200 to 400° C. (Block 4A and 4B) forming hydrocarbon vapors. The hydrocarbon vapors from thermal cracking (Block 4) is then passed to the catalytic cracking (Block 5) which is preferably arranged vertically about 20-30 mm above the thermal cracking zone (Block 4, FIG. 2 and FIG. 3 (130)). Catalytic cracking of previously formed vapors occurs in the presence of zeolite catalyst impregnated with a transition metal selected from the group consisting of Fe, Cu, Co, or Ni at temperature range of 300-400° C. Condensing the hydrocarbon vapors (Block 6A) at a temperature of about −5 to about 15° C. (Block 6) forming fuel-like hydrocarbon having C5 to C28 hydrocarbon fractions; wherein 60-80% of fuel-like hydrocarbon formed are liquids and 20-35% are gases. The condensed liquid from Block 6 formed can be collected in an air tight glass bottled for further analysis (Block 8). The uncondensed gases from Block 6 can be collected (Block 7) for further analysis using GC-FID. Preferably, the uncondensed gases can be collected in tedlar bags.

The process of thermally cracking plastic waste in a thermal cracking zone (120) and then conducting a catalytic cracking reaction in a separate catalytic cracking zone (130) controls the immediate deactivation of the catalyst and leads to higher selectivity for the production of liquids in the petroleum range as compared to the formation of gaseous fraction which can also be used as a source of heat and thus, overall process supports the economic viability of the invention. Furthermore, no external hydrogen source/hydrogen donor solvent has been used during or post reaction.

The experimental results suggest that, the carbon chain length can be narrowed to C5-C28 when the zeolite catalysts were employed, as well as a significant yield of aromatics can be obtained with substantially major percentage of naphthalene indicating that the obtained liquids are fuel-like products. The physical properties of the fuel like liquid formed are comparable with the commercially available liquid fuel which shows that the liquid formed can be used as an alternative fuel. The liquid product formed is cost effective and thus, supports the economic viability of the present invention.

The process according to the present invention produces fuel-like hydrocarbons preferably that have C5 to C18 hydrocarbon fractions. The fuel-like hydrocarbon of the present invention can have a calorific value in the range of 42 to 45 MJ/kg. The fuel like liquid formed in the present invention can be directly used for the engine operation without further up-gradation.

The process according to the present invention for the treatment of waste plastic does not involve the use of any organic or inorganic solvent for the formation of fuel like liquid. Furthermore, no external hydrogen source/hydrogen donor solvent has been used during or post reaction. Thus, the process is cost-effective, simple operating, substantially no secondary pollution, energy saving and most importantly the value product formation through the safe and reliable operation. In another embodiment of the present invention, a two-stage batch reactor system for producing a fuel-like hydrocarbons from plastic waste is provided. FIG. 3 shows the two-stage batch reactor system (100) of the present invention. The two-stage batch reactor system of the present invention comprises: a thermal cracking zone (120) adapted to receive plastic waste; a catalytic cracking zone (130) arranged vertically and connected to said thermal cracking zone (120) and comprising zeolite catalytic bed (132); wherein the zeolite catalyst is impregnated with a transition metal selected from the group consisting of Fe, Cu, Co, or Ni; and a condenser (140) connected to said catalytic cracking zone (130) maintained at about −5 to about 15° C. temperature range.

The thermal cracking zone (120) is the first heating zone and is adapted to receive the plastic waste. Preferably, the spherical reactor volume of around 300-600 cm³ can be considered for the uniform heating of plastic. The thermal cracking zone (120) contains raw material in the form of plastic beads for the first step of degradation in the thermal cracking zone. In one embodiment, the plastic waste of around 10-250 g can be loaded in the reactor. The plastic waste obtained from MSW can be shredded and pelletized before feeding to the thermal cracking zone (120). The pelletized plastic waste can be fed through a hopper (not shown in figure) to the thermal cracking zone. The process of formation of vapors (122) starts in this zone from about 200 to about 400° C. An inert gas cylinder (110), preferably a nitrogen gas cylinder with 99.99% purity supplies inert gas to the thermal cracking zone (120). The inert gas can be used as an inert media to avoid the side reactions and also as a medium for vapor transfer supplies to the catalytic cracking zone (130). The flow of inert gas to the thermal cracking zone (120) can be regulated via a regulator (112) and a flow meter (114). The flow rate of the inert gas can be in the range of 0.6-3.0 L/hour.

The vapors (122) from the thermal cracking zone (120) can be passed to the catalytic cracking zone (130) arranged vertically and connected to said thermal cracking zone (120) and comprising zeolite catalytic bed (132); wherein the zeolite catalyst is impregnated with a transition metal selected from the group consisting of Fe, Cu, Co, or Ni. The catalytic cracking zone (130) is preferably vertical about 20-30 mm above the thermal cracking zone (120), having L/D ratio in the range of 70-40 mm such that there is an immediate interaction of vapor (122) from the thermal cracking zone (120) and the catalyst bed (132). Thus, the travel path of the vapors from thermal cracking to catalytic zone is short, regarding the design of the reactor system and thereby leading to immediate interaction with the catalyst bed. This also reduces the time taken for the reaction to occur in two stage process.

In this zone (130), further cracking of previously formed vapors (122) occurs. The vapors (122) are preferably continuously passed to the catalytic cracking zone (130). Temperature of the catalyst bed in the catalytic zone can be maintained between 100-400° C. for the further cracking of thermally cracked vapors. Temperature sensors (117) are connected to both the reactors (120) and (130) to the PID controller (116).

The vapors from the catalytic cracking zone (130) are allowed to pass through the condenser (140) connected to said catalytic cracking zone (130) and maintained at about −5 to about 15° C. temperature range. A cryostat (118) can be used which behaves as a source for cooling media to the condenser (140). A gas outlet is connected where the uncondensed gases are released and collected (150) for further analysis in gas chromatograph. The uncondensed gases can be collected in tedlar bags. The condensed vapors can be collected in the form of liquid (160) at room temperature.

The two-step reactor design of the improved batch reactor system with two separate heating zones accounts to low power consumption for the complete degradation of plastic and thus, supports the first point towards the economic viability of the proposed process. The two separate zones for material treatment restricts the direct contact of polymer melt with the catalyst; thereby, the delay in coke formation is observed. The two-step reactor design of the improved batch reactor system of the present invention retains the reactivity of the catalysts for the longer period of time.

The two-step approach reactor set-up of the present invention also leads to higher selectivity for the production of liquids in the petroleum range as compared to the formation of gaseous fraction which can also be used as a source of heat and thus, overall process supports the economic viability of the invention. In addition, the further distillation of the crude product is not required and can be directly employed for the engine operation with the blend which is supported with the calorific value and GC-MS analysis of the product obtained.

The reactor system of the present invention has easy operation, and minimal maintenance and increases productivity and can be economical.

The examples used here in this invention are merely intended to facilitate the understanding of ways in which the embodiments herein may be practiced, however; the scope of the invention is not limited to them.

Examples

The plastics used herein are the waste plastics from the municipality. The poly-bags are collected, cleaned, shredded and then used for the cracking process. The plastic material used here in this invention has the composition of PP, LDPE, and HDPE which accounts for around 50% of the total municipal plastic waste. The novel catalyst prepared in the laboratory is used in very minimal amount. First heating zone is the thermal heating zone which is filled with the waste plastic in terms of raw material. For this zone, the spherical reactor volume of around 300-600 cm³ is considered for the uniform heating of plastic. Thermal heating zone has the waste plastic feed of around 10-250 g in the reactor. Reaction is performed in the presence of an inert atmosphere to suppress the side reactions due to oxygen in the atmosphere. The heating rate is varied from 5 to 30° C./min. Vapors formed in the thermal cracking zone are allowed to pass towards the catalytic zone in continuous mode. In reference to the catalytic zone, the catalytic bed of as prepared zeolite catalyst (HZSM-5), impregnated with transition metals such as, Cu/ZSM-5, and Fe/ZSM-5 are equipped with bed volume of around 20-30 cm³.

In the catalytic zone, thermally cracked vapors are further cracked catalytically for the controlled formation of vapors. Temperature of the catalyst bed in the catalytic zone is maintained between 100-400° C. for the further cracking of thermally cracked vapors. The catalytically cracked vapors are allowed to pass through the helical coiled condenser maintained between −5 to 15° C. temperature range for the condensation of the higher hydrocarbons formed in the heating zone.

The condensed vapors are converted into fuel like liquid and are collected at the bottom in the barrel. Uncondensed gases pass through the gas sampler for further testing through gas chromatography.

Table 1 shows the liquid yield percentage for the plastic mixture with higher selectivity of liquid range hydrocarbons for modified zeolites.

TABLE 1 Liquid Calorific Sr. Yield Selectivity (%) Value No. Feed Catalysts (%) C5-C12 C13-C18 C19-C28 (MJ/kg) 1 PP + — 70 15 19 58 38.45 LDPE + HDPE 2 PP + HZSM-5 60 30 46 12 40.39 LDPE + HDPE 3 PP + Cu/ZSM-5 65 38 40 8 41.16 LDPE + HDPE 4 PP + Fe/ZSM-5 65 45 42 5 42.78 LDPE + HDPE

The quality of the fuel like liquid formed is enhanced greatly with the application of two-step approach for plastic degradation. A two-step approach has the advantage of simple operation, easy to handle, cost effective, less power consumption and can be considered as an economically viable process. 

1. process for the production of liquid hydrocarbon from plastic waste comprising the steps of: (i) thermally cracking plastic waste in a thermal cracking zone at a temperature of about 200 to 400° C. forming hydrocarbon vapors; (ii) catalytically cracking said hydrocarbon vapors in a catalytic cracking zone with a zeolite catalyst impregnated with a transition metal selected from the group consisting of Fe, Cu, Co, or Ni at a temperature of about 300 to 400° C.; and (iii) condensing the hydrocarbon vapors at a temperature of about −5 to about 15° C. forming fuel-like hydrocarbon having C₅ to C₂₈ hydrocarbon fractions; wherein 60-80% of fuel-like hydrocarbon formed are liquids and 20-35% are gases.
 2. The process as claimed in claim 1, wherein the zeolite catalyst is impregnated with copper or iron.
 3. The process as claimed in claim 1, wherein the ratio of the catalyst to plastic waste is in the range of 1:10 to 1:30.
 4. The process as claimed in claim 1, wherein fuel-like hydrocarbons have C5 to C18 hydrocarbon fractions.
 5. The process as claimed in claim 1, wherein the fuel-like hydrocarbon has calorific value in the range of 42 to 45 MJ/kg.
 6. The process as claimed in claim 1, wherein the catalyst retains reactivity for about 8-10 sets of reactions.
 7. The process as claimed in claim 1, wherein the thermal cracking and catalytic cracking reaction is completed in 10 to 25 minutes.
 8. The process as claimed in 1, further comprises the steps of separating, sizing, pelletizing and/or processing the plastic waste prior to thermal cracking.
 9. A two-stage hatch reactor system for producing a fuel-like hydrocarbons from plastic waste comprising: (i) a thermal cracking zone adapted to receive plastic waste; (ii) a catalytic cracking zone arranged vertically and connected to said thermal cracking zone and comprising zeolite catalytic bed; wherein the zeolite catalyst is impregnated with a transition metal selected from the group consisting of Fe, Cu, Co, or Ni; and (iii) a condenser connected to said catalytic cracking zone maintained at about −5 to about 15° C. temperature range.
 10. The system as claimed in claim 9, wherein the catalytic cracking zone is arranged vertically about 20-30 mm above the thermal cracking zone, having L/D ratio in the range of 70-40 mm such that there is an immediate interaction of vapor from the thermal cracking zone and the catalyst bed.
 11. The system as claimed in claim 9, further comprises an inert gas cylinder supplying inert gas to the thermal cracking zone.
 12. The system as claimed in claim 9, further comprises a hydrocarbon gas collector and a hydrocarbon liquid collector connected to said condenser. 